Method and apparatus for testing thermoexpansible devices



March 1,1949. F. B. HOCKER 2,463,106

METHOD AND APPARATUS FOR TESTING THERMOEXPANSIBLE DEVICES Filed May 10, 1945 5 INVENTOR. r Hews 05B. #0 6/656.

Patented Mar. 1, 1949 METHOD AND APPARATUS FOR TESTING THERMOEXPANSIBLE DEVICES Francis B. Hooker, Macomb,

Globe American Corporation,

corporation Ill., assignor to Kokomo, Ind., a

Application May 10, 1945, Serial No. 593,037

4 Claims.

This invention relates to the method and the apparatus used therein for testing wafer thermostats for leakage, expanding and other characteristics, such as to render them defective in use.

Wafer thermostats for many uses are inexpensively constructed, but to function properly they must expand to certain widths or dimensions at predetermined temperatures within reasonable tolerances. It is, therefore, necessary that in production each wafer be tested to determine its expansive characteristics so that those which are defective in this respect may berejected.

The object of this invention is to provide a simple and inexpensive method and apparatus for automatically rejecting all wafers from a batch to be tested which at a given temperature and over a reasonable period of time do not expand to the required degree. This is accomplished by confining a batch of wafer thermostats within individual compartments having walls spaced from each other to the extent of the required expansion at a predetermined temper ature, heating the thermostats while in such compartments to such temperature whereby they will be expanded into frictional contact with the confining walls of their respective compartments, and then while so heated and expanded their support within the compartments is removed or the bottom inverted so that those thermostats which have failed to expand to the desired degree and into frictional engagement with the spaced walls of the compartments, will freely drop therefrom. Such thermostats may then be considered as defective and rejected, whereas those that have expanded into frictional contact with the walls of the compartments will be held in place and will thus pass the required test.

The full nature of the invention will be understood from the accompanying drawings and the following description and claims:

Fig. 1 is a perspective view of a container for supporting the thermostats in confining compartments.

Fig. 2 is a cross section taken through the container.

Fig. 3 is a central vertical section through a heating cabinet with a plurality of containers mounted therein for raising the temperature of the thermostats to the required degree.

Fig. 4 is a longitudinal section through the container showing the expanded wafers in elevation retained therein while defective wafers drop therefrom.

In the drawings there is shown an insulated heating cabinet l0 provided with heating elements I l electrically connected through the lines l2 with a suitable source of current, whereby the cabinet may be heated to a predetermined temperature controlled by a thermostat 13 mounted therein, which thermostat is in circuit with the heating elements H.

The cabinet I0 is arranged to receive a plurality of containers or drawers M which may be readily removed from the cabinet when open. The cabinet is shown herein with its closure removed, but it will be understood that when the containers or drawers I4 are in place, the closure may be secured in any suitable manner to seal the cabinet during the period of heating.

The container 14 provides a support for a plurality of wafer thermostats 15 to be tested. These thermostats are disk-like and are arranged standing upon edge within individual confining compartments l6. Each compartment comprises a pair of spaced walls ll of a prescribed distance apart. Also each compartment is spaced from the adjacent compartments.

The walls forming the compartments are arranged and maintained in their proper spaced position by a series of spacing rods I8 extending longitudinally of the container and supported at their opposite ends by the ends of the container as illustrated. For convenient placement and removal of the thermostats within their compartments, the forward wall I! of each compartment is recessed at l9 to provide a wafer stud receiving slot.

Wherein the thermostat should expand to a prescribed depth, at a temperature of degrees F. for example, the walls I! of the compartments are spaced slightly less than such prescribed depth so that upon being heated to such temperature the expansion will cause the thermostats to slightly and frictionally engage the walls sufficiently to hold them in place within their respective compartments. Thus, the temperature of the cabinet may be raised to 110 degrees F. and held by the thermostat I3 to that temperature for a determined period of time, the preferable testing period being seventytwo hours. At the end of the testing period the cabinet is opened and the containers l4 removed therefrom and immediately inverted, as shown in Fig. 4. Those thermostats which have properly responded to this temperature will be held in their compartments by their friction contact with the walls l1. But those thermostats which have not properly expanded because of leakage hold them in place if they possess theprescribed amount of expansion when heated to a predetermined temperature, heating theitray, supporting the devices to a predetermined temperature, and

inverting the tray while at such predetermined temperature, whereby any devices which do not have the prescribed amount of expansion will drop out by force of gravity.

2. A method of testing a thermo-expansible device to determine whether it will expand ,a predetermined amount for a predetermined increase of temperature comprising, placing the device in a compartment open at the top and having walls spaced apartsuch distance that the device will normally lie loosely therebetween but, will frictionally engage the same upon a u prescribed amount of expansion when heatedto a predetermined temperature, heating the devicetoua predetermined temperature, and inverting its compartment While at such predetermined. temperature, whereby itwill frictionally engageand remain between saidwalls if expanded said prescribed amount and Will drop therefrom by gravity if ineffective to frictionally engage said walls.

3. A method of testing thermo-expansive devices consisting in placing said devicesto betested in individual compartments having an initial support therefor and confining walls spaced apart a distance so that said devices will normally freely lietherebetween, heating said devices .toa predetermined temperature so as to expand those 10 a distance so that the devices fit loosely therebetween but will frictionally engage the .same todevices of proper expansive characteristics into frictional engagement with said walls, and thereupon relieving those devices that have not sufficiently expanded into such frictional engagement of their initial support and permit them to drop from said compartments by gravity while those of proper expansion characteristics will be frictionally supported therein by said walls.

4. A testing apparatus for determining the ex- ;pansion characteristics ofgthermo-expansible devices upon being heated to a predetermined temperature comprising a container open at the top and having a bottom support for receiving and supporting a plurality of said devices to be tested, said-contai-ner being divided into a plurality of confining compartments, each comprising a pair of side walls spaced a predetermined distance from each other'to individually receive therebetween oneofsaid devices, and rods supported at their ends in said container carrying spacing elements for. engaging and maintaining .said wallsin predetermined spaced relation to be frictionally engaged by those devices having a prescri-bed expansion upon being heated to apredetermined temperature to thereby retain said devices upon said container being inverted.

FRANCIS B. HO.CKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES" PATENTS Number Name 1 Date 256,640 Clark Apr; 18, 1882 386,383 Connable- July-1'7, 1888 456,630 Morse ;Ju ly 28, 1891 1,308,821 Tripp "(July-,8, 1919 1,661,323 Crosthwait, Jr. -Mar.'6,- 1928 1,694,164 Crosthwait, Jr. Dec. 4, 1928 2,081,078 Watson May:18, 1937 2,095,355 Cate Oct.-12, 1937 

